In Colombia, the structural design of rigid pavements is based on the concrete modulus of rupture (MR), so selecting an appropriate mix is crucial to ensure reliable slab performance under fatigue (INVIAS, 2022; NRMCA, 2014). This study presents a comparative analysis of the flexural behavior of four hydraulic concrete mixtures for rigid pavements, industrially produced with local aggregates from the Rosapamba quarry (fine) and the Agrebases quarry (coarse), with water–cement ratios between 0.58 and 0.61. For each mixture, the aggregates were characterized in accordance with Colombian highway specifications, 16 compression tests and 16 flexural tests were performed at 28 days, and descriptive statistics, analysis of variance and regression models were used to relate MR to the water–cement ratio and to compressive strength (fʼc) (INVIAS, 2022; R Core Team, 2022).

Average compressive strengths ranged from 29.6 to 31.0 MPa, while mean flexural strengths varied approximately between 3.8 and 4.1 MPa, thus satisfying the design MR in all cases (INVIAS, 2022). The mixture with a water-cement ratio of 0.58 reached the highest mean MR (4.1 MPa), with a strength reserve close to 10% with respect to the target value, whereas mixtures with water-cement ratios from 0.59 to 0.61 were located very close to the 3.8 MPa threshold, with smaller margins but still consistent with medium-strength pavement concretes (Neville & Brooks,  2010; Mehta & Monteiro, 2014). Global MR/fʼc ratios were found in the 0.12–0.14 range, in line with studies that place flexural strength between 10% and 20% of compressive strength, indicating that mixtures with local aggregates follow a mechanical pattern compatible with internationally accepted empirical relationships (NRMCA, 2014; Yusuf, I. (2016).

The analysis shows that the mixture with a water-cement ratio of 0.58 provides the most robust structural response, while mixtures with ratios of 0.59 and 0.60 represent an adequate compromise between mechanical performance and efficient cement use in rigid pavements for regional roads in southwestern Colombia (INVIAS, 2022; Mehta & Monteiro, 2014).